New thermostat

Hi all.

Have just replaced my old Honeywell stat for a Horstman DRT2 programmable replacement which hopefully having figured the wiring ok worked great for a week.Now when it asks for heat it blows the fuse at the boiler so have had to put the old one back on. Must admit i was expecting only two wire connection from the timer but did actually have three to sort and worked fine for a week?? Was wondering if maybe this stat isn't compatible with my system which is about 16yrs old and a conventional non combi system ? any help much appreciated.

try discronnecting your water pump. and try again

it may be a coincidence but your pump may be forked.?

how did you connect the new stat? it should be live in from timer to com, live out connected to nc and the neutral made safe ie not connected.

Many thanks for that,i did have it wired differently ie red to no,yellow out to com and blue neutral to nc....worked ok for a week though ? Will have another go later when i get home